And it shall come to pass, when I bring a cloud over the earth, that the bow shall be seen in the cloud. And I will remember my covenant, which is between me and you and every living creature of all flesh; and the waters shall no more become a flood destroy all flesh. And the bow shall be in the cloud; and I will look upon it, that I may remember the everlasting covenant between God and every living creature of all flesh that is upon the earth. – Genesis 9:14-16
God creates memorials* that He, too, might remember! And perhaps because He wants those same memorials to remind us, as well.
As God looks upon the bow, that he may remember the covenant, so should we, that we also may be ever mindful of the covenant, with faith and thankfulness. – M. Henry
* MEMORIAL – Something which serves as a reminder. Scripture witnesses to God’s participation in human history for the salvation of God’s people. Memorials to such events reinforced faith and provided opportunities for teaching. God’s covenant name (Yahweh) was to be a “memorial name” (Ex. 3:15 NAS), a reminder of God’s liberation of God’s people. The Passover served as a similar reminder (Ex. 12:14; 13:9). The twelve stones taken from the Jordan’s bed served as a reminder of God’s provision of passage across the Jordan (Josh. 4:7). In the New Testament, the Lord’s Supper serves as a reminder of Christ’s sacrificial death and an encouragement of His future coming (Matt. 26:13; Mark 14:9; I Cor. 11:25-26). All these memorials serve to “proclaim” the good news of what God has done.
-- Holman Bible Dictionary